Oil to be used must not attack sealing Rings. Generally oil used for main propulsion unit is SAE 30. Remove screw plug and fill up the stern tube oil. Oil pressure must amount to only 0.2 – 0.3 Kg/cm² more than SW pressure. Preheated to 60 – 70°C when viscose oil is used or low temperature prevails. Remain in this condition for several hours (says overnight) and turn engine by Turning Gear to change the shaft position 3 – 4 times. Check oil leakage from Drain Plug and if it is all right, fit back Drain Plug and fill oil from venting and Filling Plug and close. Forward Seal is fitted .